A review on pathogenicity of Aeromonas hydrophila and their mitigation through medicinal herbs in aquaculture.

Aeromonas hydrophila is a freshwater, facultatively anaerobic, chemo-organoheterotrophic bacterium that distressed fishes with gastroenteritis, septicemia and causes a disease known as Motile Aeromonas Septicemia (MAS), which affects the aquatic environment. Haemolysin, aerolysin, cytosine, gelatinase, enterotoxin and antimicrobial peptides have been identified as virulence factors in A. hydrophila. Medicinal herbs/plants and their uses are the instant, easily available, cost-effective, efficient and eco-friendly approach for socio-economic, sustainable development of modern aquaculture practice. Phytotherapy either through a dip or by incorporation into the diets is an alternative approach to synthetic pharmaceuticals to diminish the pathogenicity of aquatic environmental pathogens. Due to the presence of remarkable phytoconstituents like flavonoids, alkaloids, pigments, terpenoids, steroids and essential oils, the medicinal plant exhibits anti-microbial, appetite-stimulating, anti-stress, growth-promoting and immunostimulatory activities. Aqua-industry preferred phytotherapy-based techniques/compounds to develop resistance against a variety of aquatic pathogens in culturable fishes because they are inexpensive and environment-friendly. As a result, this review elaborates on the diverse applications of phytotherapy as a promising tool for disease management in aquaculture and a major step toward organic aquaculture.

Evaluation of the acute toxicity of Thymus linearis ethanol extract and its effect on the hemato-biochemical and behavioural response of the Golden mahseer, Tor putitora (Hamilton, 1923).

The present investigation was conducted to estimate the acute toxicity of Thymus linearis plant extract, its effect on hemato-biochemical parameters and behavioural response in the golden mahseer (Tor putitora). The phytochemical composition present in T. linearis plant extrat were Alkaloids, Flavonoids, Phenols and Tannin. The fishes were subjected to eight different concentrations of T. linearis leaves extract (8.25, 8.50, 8.75, 9.00, 9.25, 9.50 and 9.75 mg/kg) and the control group without plant extract for 96-h LD50 study. The mortality was recorded every 24 h post-treatment. Minimum mortality was recorded in the 8.25 mg/kg, whereas 100% mortality was recorded in the 9.75 mg/kg T. linearis extract after 96-h periods. The LD50 was estimated by probit analysis, and the value of T. linearis at 96 h was found to be 8.71 mg/kg for golden mahseer. A non-lethal dose of 1/10th of 96-h LD50 value (0.87 mg/kg) was taken for the sublethal study. After 96 h, the red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb), packed cell volume (PCV) and blood glucose were measured. RBC (×106/mm3), Hb (%) and PCV (%) significantly decreased at 8.25, 8.50, 8.75, 9.00 mg/kg, but WBC and blood glucose significantly increase at 8.25, 8.50, 8.75, 9.00 mg/kg of T. linearis plant extract. The observations on behaviour response of golden mahseer were also recorded. In the present study, the acute toxicity of wild ajwain was more significant than short-term toxicity. The mortality rate was very high during the study period of T. linearis exposure.